cure between layers?

when you first coat the fleece...or whatever material you use with resin, do you have to wait for it to cure before you start laying the mat/resin? also, do you have to let each layer of mat/resin cure before adding more? if so, how long?

It depends on the mixing ratio of the catalyst to resin. If you mix it up hot (too much catalyst to resin) then the working and curing time is sped up however this can cause problems. The opposite can happen when a lower ratio is used (too little catalyst to resin). It will greatly slow down or extend the curing time or not cure at all. Normally I mix mine a tad hot in cooler weather and use less catalyst in hotter weather. You will find out that fiberglassing is a chemical reaction and creates heat. You first mix it up and put it on and it's nice and cool or at room temperature. Wait a while and it heats up. Wait a while longer and the temperature will go back to your room temperature. That is when you should add the next layer. If you add another layer to a heated layer it will kick faster and now both could work against each other and create warping/cracking issues. Like anything else the more you do the better you will get (or at least you should get better). You learn by doing.

Jim 

I ditto Jim and Jeff.  I let the first layer fully harden and cure.  When this first layer has kicked off heat and fully returned to room temperature, I scuff it with 80 grit completely.  I lay the second layer.  Right after this layer gets near room temp, I lay the next layer, and the next layer, and the next.....like Jim explains.  However, I have noted that when its about 80°F and humidity is higher than 65ish you can start additional layers a little after heat is kicked off, which in this case has decreased overall process time.  But you gotta mix correct and work FAST.  Take advantage of it if you can.

Uh, again, I ditto JIM......    "Like anything else the more you do the better you will get (or at least you should get better). You learn by doing.

JD